Which fictional drug is worse?
 

Crystal Twist from C.O.P.S. (Central Organization of Police Specialist! the animated one not the dumb reality show).

Spark from GI Joe.

Bliss from Captain Planet.

Nuke from Robocop 2.

Spin from Bravestarr.

He-Man and the Masters of the Universe
 

There was also one from He-Man and the Masters of the Universe that Elena took.

Hyper-M in Sharivan Next generation was pretty bad. It was a pain-suppressing narcotic that, while would give a boost in power, would end up killing the user.

MGH in the Marvel comics. A literal temporary mutant power, but can have horrifying effects depending on what mutant the hormones were pulled from. One turned a kid to crystal, and his arm was shattered shortly afterward. Guess what happened after it wore off...? There were others that were equally horrific. Nasty drug, made to give users the high of experiencing superhuman powers. And highly addictive.

Slo-Mo from Dredd

I remember something like Brain Boosters from Galaxy High, they like make you super smart on a chosen subject but using too much can leave you brain dead. If course main character got better the moment he dropped it.

All pretty bad drugs but who else thought the Captain Planet and Bravestarr drug episodes were sad?